Gelatin, a collagen derivative, is utilized in various facets of food, photographic and medication production. Gelatin is a primary ingredient of gel type desserts, marshmallows and the like. It is also utilized in the production of capsules for time release ingested medication and emulsion gels in photographic applications. In almost all instances, commercial viability of the gelatin is determined by its rigidity or gel strength, with higher gel strength being most desired.
The standard measurement of gel rigidity is known as Bloom strength and it is defined as the weight, in grams, required to make a 0.5" (1.27 cm) diameter, flat bottomed plunger depress the surface of a gelatin gel 4 mm. The weight is applied in grams of lead shot and generally ranges between 100-300. Commercially desirable gelatin has a production line Bloom strength which generally ranges between 250-260.
The rigidity of the gelatin gel is directly related to its proline and hydroxyproline content. Accordingly, extraction methods, from various gelatin sources, must preserve some measure of the proline and hydroxyproline content in order to produce gelatin with acceptable Bloom strength levels.
Gelatin, in relatively high yield and of high Bloom strength, is commonly economically produced from bones and hides of animals and particularly from pigskin. The collagen contained therein is converted to gelatin by alkaline or acid pre-treating, typically by immersion in baths with periodic aeration mixing, for extended periods of time. A common pretreatment method which provides relatively high yield (10-15%) and high gel strength (Bloom strength of 250-260) in commercially available animal derived gelatin, is treatment with strong alkaline solutions for about sixty days prior to extraction. Alternatively, the bones and hides are treated with hydrochloric or sulfuric acid for the extended periods of time. Gelatin extraction thereafter, results in readily discernible type A and type B gelatins depending upon whether there was an initial acid or alkaline treatment.
The standard extraction methods involve neutralizing the alkaline or acid treated bones and hides and placing them in a neutral water bath. The temperature of the bath is brought to a level in the range of 50.degree.-60.degree. C. (lower temperatures result in lower yields and incomplete extraction and higher temperatures tend to degrade the gelatin production or the quality of gelatin being produced) with the solid gelatin being extracted into the water. At monitored levels of solids forming in the water, typically 5%, additional steps of filtering and drying are effected to purify the extracted gelatin and to raise the levels, in stages, to about 30-32%. At this point, the extraction is considered complete and the water containing gelatin is dried, and the solid gelatin is granulated and ground to specifications.
For religious or other reasons, there are substantial segments of the populace, e.g. orthodox Jews, Moslems, vegetarians, etc. who find the common animal sources of gelatin as being inimical with their beliefs. Accordingly, other gelling materials have been utilized for foods and medication for such members of the populace. An example of a common, alternative non-animal gelling material is agar agar, a seaweed derivative. Gelling strength of such alternative materials has however been mediocre (equivalent to Bloom strength of about 100-200), and palatable sources of gelatin, other than the common animal derivatives have been sought.
Methods for the extraction of gelatin from fish; in particular fish having fins and scales (kosher fish), a more palatable source for orthodox Jews; Moslems and many vegetarians, have been known for some years. In such methods the collagen rich fish skins (particularly of warm water fish species) and to a lesser extent, swim bladders, are treated, to form and extract gelatin. However, the efficacious extraction methods, commonly utilized with the animal sources for gelatin, particularly the alkaline methods, for extended time periods, tend to result in unusable fish skins and swim bladders, with little, if any, extractable useful gelatin. In particular, such methods do not allow for extraction prior to putrefaction of the fish. Fish, particularly species with high fat content, are highly susceptible to rapid bacteria development and putrefaction after only short time periods. Furthermore, gelatin extracted from fish is susceptible to an objectionable characteristic fish smell, associated, in part, with even small degrees of putrefaction.
With many acid based extraction methods, including the ones presently being commercially utilized, the collagen found in many fish has exhibited significantly lower levels of hydroxyproline and proline with relatively lower gelling strength, than required for real commercial viability. In addition, gelatin yield, with acid based extraction methods, even under the most ideal laboratory conditions, rarely exceeds 15%.